Subdivided service system of radio broadcast distribution



July 21, 1931.

SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCAST DISTRIBUTION SHORT WAV E E. E. CLEMENT Filgd J1me 28. 1924 MODULATOR LONG WAVE ObuLLATOR 514021 WAVE mmaumme Aumo MODULATOR Lone wAve RADIO 0R awn-M1010 MODULATOR.

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July 21, 1931. E. E. CLEMENT 1,315,833

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E. E. CLEMENT SUBDIVIDED SERVICE SYSTEM OF.RADIO BROADCAST DISTRIBUTION Filed June 28, 1924 TUNED T0 mnumwm'z :mom WAVE.

TUNED To INTERMEDIATE LONG WAVE 4 Sheets-Sheet 4 RADIO AMPLIFIER AND TRANoMrl'TlR LONG WAVE RADIO AMPLIFlKR Patented July 21, 1931 UNITED STATES PATENT OFFICE EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR T EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCAST DISTRIBUTION Application filed June 28, 1924. Serial No. 722,993.

My invention relates to systems of radio say from 1,000 to 3,000 kc. The doubly modbroadcast distribution, and has to do parulated short waves are picked up at the local ticularly with such systems as involve regionor regional distributing centers, where the al distribution among local or subscribers short wave carrier is eliminated, the long stations. It has for its object the produc wave carrier is amplified and relayed to the 55 tion of a system and a method of operation by subscribers in that area, preferably over their which the entire broadcast field may be diwired circuits. At the same time, the subvided into local areas served by their own scribers can tune for the short wave carrier 7 regional distributing centers, and the genfrom the distant or primary station, and the 10 eral broadcasting may be by selected prilong waves distributed to them over the wires 0 mary stations, supplemented by local prowill then act as boosters, being in perfect grams and local broadcasting, as at present. synchronism, and in fact identical with the In such a system it is essential that the sublong wave modulations which the subscribscribers instruments be standardized for ers receive with greater or less eflieiency on economy and efliciency, and that said instruthe short wave side of their instruments. ments be made as simple as possible. It is As a variation of this method, the regional therefore a supplemental object of my indistributing centers may filter out and disvention to make the subscribers instrument tribute the modulated long waves to their as simple as possible, to standardize it both subscribers, and at the same time may am- 20 in structure and in operation, so that for plify and relay modulated short waves either local or long distance receiving it will through the ether. This however, is a refinerequire very little manipulation, and will be ment, and not an essential part of the invenabsolutely certain to produce good results. tion, the gist of which lies in standard trans- In order to attain my object, I preferably mission on short waves, the filtering out and connect my subscribers stations to local or distribution preferably through wires on regional central stations by means of line modulated long waves, and the standardizwires, which may be telephone, telegraph, ing of the subscribers instruments, which electric light or power wires, preferred in whether receiving local or'long distance matthe order stated; provide each subscribers ter, will always be efiicient, because they will so station with asimple form of radio receiving always have the modulated long waves to instrument having a detector and if desired serve as boosters for any energy Waves they one stage of audio amplification; provide each may receive from a distance.

local central station with means for receiv- It is true that so far as practicable operaing, detecting, and amplifying at radio tion is concerned, distribution to the subscribfrequency signals from a distance; and finers could be confined to the long waves over ally provide primary stations (and if dethe wires, but this would deprive the system sired also local central stations) with transof the interest and value inherent in genuine mitting means by which both a long wave radio receiving by the subscriber. The ideal carrier and a short wave carrier can be method of operation is to permit the sub- 4 transmitted, preferably by double modulascriber to tune for all distant stations, and tion, and at the regional central stations the to know he is getting them, which is the fact; long wave carriers with the modulations can to provide at all times enough booster energy be distributed to the subscribers over their in the long waves distributed from each local wired circuits after amplification. More central, so that the actual receiving at every specifically stated, I provide a primary stasubscribers station will be fully equal in tion with means for imposing modulations results, even of the most distant stations, to which are to be distributed to the subscribthat obtainable with the most advanced and ers, upon a long carrier wave, at say 20 kc; powerful apparatus, if operated independthen imposing this 1on modulated wave as ently.

59 a modulation upon a short wave carrier, at T e same principle is involved in this sys tem as in that of my prior application Serial No. 701,123, filed March 22, 1924, patented January 6, 1925, No. 1,522,362, in which I described and claimed the use of superheterodyne receivers at the central stations,

whereby frequency transformation was rendered possible, and the modulated long waves could be amplified and distributed to the subscribers. In the present case, however, heterodyning is not an essential feature.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 shows the equipment of a primary station for transmitting at double modulation.

Figs. 2 and 2a show the circuits of a regional central ofiice or relay station, for receiving the doubl modulated wave from the transmitter of ig. 1, detecting and amplifying the long carrier wave and distributing it to the subscribers substations where it is demodulated for the audio signals.

Fig. 3 is a diagram of a system for detecting the long wave of Fig. 1, at a regional central ofiice or relay oflice, and distributing it by wire to subscribers substations where it is demodulated together with the long waves demodulated 'from short waves received directly at the substation by radio transmission.

Fig. 4 is a diagram of a system for transmitting a doubly modulated wave the same as that of Fig. 1 with the additional feature that the same audio modulations are also put directly on the short wave.

Fig. 5 is a modification of the subscribers radio receiving set of F i 3 in which the long and the short waves of Fig. 4 are separately demodulated and the audio modulations combined through a triple winding audio transformer.

Fig. 6 is a modified arrangement of the system of Figs. 4 and 5 in which the subscriber is furnished with a common audio modulation of two frequencies, one received directly by radio from a transmitting station and a lower frequency received by wire in the form of a long wave beat resulting from heterodyne reception at the central oflice of the short wave from the same transmitting station.

Fig. 7 is a diagram of a further modification for distributing short and long waves with common modulations as in Fig. 6.

Fig. 8 is a diagram of an arrangement for radio transmission, by double modulation, of 55 a short and a long carrier wave both bearing a common modulation.

Fig. 9 is a diagram of a system for receiving at a regional central otfice or relay station, the primary or doubly modulated wave trans- 60 mitted by the system of Fig. 8 separately and filtering or demodulating out the two carrier waves amplifying and distributing them to the subscribers, the short waves by radio and the long waves by wire.

Referring to the drawings in general, and

referring to Fig. 1, this shows a system for radiating a doubly modulated wave using Heising method of modulation. It consists of a transmitting antenna 1, excited by a radio or high frequency oscillator D, the output of which is modulated by the modulator C, according to the well known Heising method, with a long wave produced by a long wave oscillator B coupled to the oscillator C by the inductance coupling 2, the oscillations of the oscillator B being in turn modulated with audio signals from the transmitter 3 through the modulator A. This system for transmission at double modulation is the same as that illustrated and described in the publication Principles of radio communication, Morecroft, John IViley and Sons, London, 1921, pp. 681-682. In the operation of the transmitter shown in Fig. 1 audio signals originating at the telephone transmitter 3 act through the modulator A to modulate the oscillations of the long wave oscillator B which oscillations are modulated through the modulator C on to the short carrier wave produced by the oscillator D and radiated from the antenna 1.

In Figs. 2 and 2a are shown a receiving system situated at a regional central ofiice, such as thetelephone exchange system, for receiving the waves transmitted by the system of Fig. 1, above described, and distributing the signals borne thereby to subscribers substations. This system of reception and regional distribution consists of receiving an tenna 4 with which is operatively connected, as shown, a detector 5 having its input circuit 6 tuned to the primary wave generated by the oscillator D of Fig. 1 and its output circuit 7 coupled to the first of a series of amplifiers 8 and 9 through an input circuit 10 tuned to the intermediate frequency generated by the oscillator B of Fig. 1. The amplifiers 8 and 9 are coupled as usual through a suitable inductive coupling 11, the last amplifier 9, being coupled through the inductances 12 and 13 to a subscribers line 14 preferably tuned at both ends. The central station end in Fig. 2 is tuned by means of the inductance 13 and variable capacity 15 while the subscribers end, Fig. 2a, is tuned by the variable inductance 16 and variable capacity 17. The telephone line 14 terminates at the central office, Fig. 2 in any well known or other suitable telephone line terminal apparatus indicated symbolically by the telephone line jack 18, and terminates at the subscribers substation, Fig. 2a, in any usual or other well known telephone instrument indicated symbolically at 19. The subscribers station Fig. 2a is also provided with a radio receiving set 20 consisting of the detector 21 having its input circuit 22 inductively coupled to the line through the inductance 16 and tuned to the long or intermediate carrier wave, its output circuit being connected to suitable audio receiving means such as the telephone headset 23, which of course, may be substituted by any well known or other suitable form of connecting means such as a loud speaker unit with the necessary additional stages of amplification.

In the operation of the receiving system of Figs. 2 and 2a, in the reception of audio signals set out by the transmitting signal of Fig. 1 the short or primary carrier wave is received through the antenna 4 and tuned coupling and input circuit 6 and detected or demodulated by the detector 5 to take out the intermediate carrier wave which is amplified through the amplifiers 8 and 9 connected in cascade, and sent out over the line 14 to the subscribers substation of Fig. 2a where the said long or intermediate carrier wave is transferred through the inductance 1622 to the subscribers radio receiving set and demodulated by the detector 21 to reproduce the audio modulations in the receiver 23.

To enable the subscriber to receive the matter transmitted by the system of Fig. 1 both directly by radio and from the central distributing station by wire, the apparatus at the subscribers substation may'take the form of that indicated diagrammatically in Fig. 3, in substitution of that indicated in Fig. 2a. The subscribers apparatus of Fig. 3 is the same as that of Fig. 2a except that in addition to the wire radio receiving set 20 an independent radio receiving set 24 is provided having a detector 25 with an input circuit 26 tuned to the short or primary wave and coupled to the subscribers individual receiving antenna 27. The output or plate circuit of the detector 25 is inductively coupled to the subscribers tuned input circuit 22 through inductance 28. As the input circuit 22 of the subscribers detector 21 is tuned to the long or intermediate wave it acts through its inductive coupling with the inductance 28 to cause the detectorflb 'to detect or demodulate the long or intermediate wave out of the short wave received on the antenna 27 and combine it with the same long wave received over the line which combined wave energy is demodulated by the detector 21 to reproduce the audio modulations in the receiver 27. To enable a subscriber to tune in on and receive matter by radio directly from the transmitting station of Fig. 1 or some other station transmitting on double modulation with substantially the same intermediate wave length, means are provided such as the switches 29 and 30 for disconnecting the subscribers telephone line from his radio receiving set thus leaving the subscriber free to tune in for dif ferent short wave stations without either help or interference from the central oflice but with reduced volume of reception, especially in reception of signals from distant stations.

Thus with the subscribers receiving set of Fig. 3, used with the radio and Wire distributing system of Figs. 1 and 2, the subscriber is enabled to either tune in for himself and receive the broadcast independently of the exchange or have the volume of his radio reception boosted from the central oflice by the long waves transmitted over his telephone line.

A modified arrangement for double modulation transmission which may be substituted for the transmitting system of Fig. 1 is shown schematically in Fig. 4 which indicates a transmitting system identical with that of Fig. 1 in all respects except that the same audio modulation that is put on the long or intermediate wave is also put on the short or primary wave. The purpose of this arrangement is to enable a party receiving by radio to either filter out the long wave and take the modulations from it or take the audio modulations directly from the short wave. To enable a subscriber to receive on the short wave and combine the common audio modulations detected directly from it with the common audio modulation-s sent by long carrier wave over his line circuit by the system shown in Fig. 2, I provide the subscribers receiving circuit as shown diagrammatically in Fig. 5 which is the same as that of Fig. 2a, with an additional radio receiving'set 31 having its audio output circuit connected in common with the audio output circuit of the line set 20 to the telephone receivers 23 through a triple winding audio transformer 32.

In the operation of the subscribers circuit of Fig. 5 in combination with the radio broadcast system of Fig. 4, and a relay wire distributing system of Fig. 2, the subscriber may receive the short wave directly by radio from the broadcasting station of Fig. 4 or any one of a number of stations like it, independently of the wire distributing relay system of Fig. 2 by tuning the input circuit 33 of his detector set 31 to the primary or short wave of the desired station, the short wave being demodulated by the detector 34 to put the audio modulations through the coil 35 of the triple winding audio transformer 32 which modulations are transferred by induction to the output winding 36 and receivers 23. By closing the switches 29 and 30, (Fig. 5), the subscriber may have the volume of reception boosted from the central ofiice (Fig. 2) by the long wave received by radio from the sending station of Fig. 4 and transmitted over the subscribers line with the common modulation-s in the same manner as that described for Figs. 2 and 2a except that the audio or output circuit of the detector 21 is connected through the winding 37 of the triple winding transformer 32 so that the common modulation detected by the detector 21 is combined with that of the detector 34 thus boosting the volume of the signals received in the telephone receivers 23.

Fig. 6 shows a further modification enabling the subscriber to receive the same signal modulation by either radio or wire or both radio and wire. In this arrangement signals are sent from a primary station 38 on the usual signal modulated short wave received at the subscribers substation 39 through the antenna 40, tuned input circuit 41, short wave detector 42, primary winding of the triple winding induction coil 32, output winding 36 and telephone receivers 23. In this system the same signal modulations are sent to the subscriber over his line 14 by a long carrier wave resulting from heterodyne reception of the modulated short .wave from the transmitter 38. The subscriber may thus receive a booster effect over his telephone line as follows: The radio broadcast from the transmitter 38 is received at the telephone central station 43 through the superheterodyne receiving set 44 in the usual manner well known in the art except that the intermediate or beat frequency is transmitted through the coupling circuit 45 over the subscribers line 14 to the subscribcrs substation 39 where it is taken off through the coupling connection 1622, demodulated by the subscribers detector 21, and the modulations put through the primary winding 37 and thus added to the signal furnished through the detector 42.

In Fig. 7 is shown a further modification of a system for transmitting a common modulation by both radio and wired carrier current which may be substituted for that portion of the system shown in Fig. 6 above the dotted line 46. According to this arrangement both the short wave carrier and the long wave carrier are transmitted from the central station with a common modula tion. It consists of a telephone transmitter 47 operatively connected through suitable source of current 48 and transformers 49 and 50 to separate modulators 51 and 52, the modulator 51 being operatively connected to a short wave radio transmitter 53, while the modulator 52 is operatively connected to a long wave transmitter 54 having its output circuit coupled through a suitable coupler 55 to the subscribers line 14. The subscriber whose substation apparatus is identical with that of Fig. 6 may thus receive the signal originating at the transmitter 47 by either pure radio or wired radio or a combination of both in the manner similar in all respects to that described in connection with Fig. 6.

In Fig. 8 signals originating at the transmitter 56 are impressed, through the modulators 57 and 58 upon the oscillations produced by the short and long intermediate car rier wave oscillators 59 and 60, respectively, the oscillations of which are impressed, through the modulators 61 and 62, respectively, upon the oscillations of the short or primary carrier Wave radio transmitter 63.

Fig. 9 shows a regional distributing system for receiving at a distance the matter transmitted by the transmitter system of Fig. 8 and regionally distributing the same by both radio and wire to subscribers. of a receiving antenna 64 and antenna coupling inductance 65 to which is coupled the tuned input circuit 66 of a detector 67, input circuit 66 being tuned to the short or primary wave transmitted by the transmitting system of Fig. 8. The output circuit of the detector 67 is coupled through inductance 68 to a pair of filter circuits 69 and 70 tuned respectively to the short intermediate wave and the long intermediate wave and connected to the input terminals of the detectors T1 and 72, respectively. The output circuit of the detector 71 is connected by a suitably tuned transformer coupling 73 to a radio amplifier and transformer 7 4 connected to the transmitting antenna 75 for radiating short waves. The output circuit of the detector 72 is connected through a suitably tuned transformer 76 to the input side of a long wave radio amplifier 77 whose output circuit is connected to the subscribers line 14 through the inductive coupling 78. In the operation of this receiving and transmitting system the short primary carrier wave transmitted by the transmitting system of Fig. 8 is received on the antenna 64 and demodulated by the detector 67 to put the intermediate carrier waves through the inductance 68 from which the intermediate short wave is picked up by the tuned circuit 69 and detector 71, transferred to the radio amplifier transmitter 74 and radiated out through antenna 75, while the intermediate long wave is picked up by the tuned circuit 70 and detector 72, transferred to the long wave amplifier 77 and distributed over the subscribers line such as the line 14. For reception of the two waves with common modulations distributed as above described, the subscribers circuit indicated below the dotted line 46 of Fig. 6 is used, the operation for reception being identically the same as described for Fig. 6.

In my claims hereinafter I shall use the terms long waves and short waves. By long waves in this case I mean waves of too low a frequency to be efiiciently transmitted by radiation, but which are well adapted for transmission by wire, as for example waves of a frequency between 25 and 100 kc. By short waves I mean waves of too high frequency to be eiliciently transmitted by wire, but which are suited for transmission by radiation, as for example waves of a frequency of 500 to 3,000 kc. per second.

Having thus described my invention, What I claim is:

1. In a wired system of radio broadcast distribution, a primary transmitting station, a secondary distributing station, subscribers stations connected to said secondary station It consists by wire lines, and means whereby modulations imposed on a short carrier wave at the primary station are resolved into modulations on a longer carrier wave at the secondary station, means to distribute said long waves over said wires to the subscribers stations, and a common receiving means for both the radio and wire transmitted waves at each subscribers station.

2. The system as claimed in claim 1 in which the means for shifting the modulations from the primary carrier wave to a longer wave includes a heterodyning oscillator at the secondary station, and a filter coupler with fixed tuning, the subscribers receiving means being tuned to the fixed frequency of said filter coupler.

3. The system as claimed in claim 1 in which the short carrier wave is doubly modulated to carry a modulated long wave at a frequency to which the subscribers receiving means are tuned and the long carrier wave distributed at the secondary station is the modulated long wave carried by the short carrier wave.

4. The system as claimed in claim 1 with means at the subscribers station tuned for receiving directly by radio from a primary transmitting station, other means for receiving the long waves by wire, and a common audio frequency receiver for both said means.

5. In a wired system of radio broadcast dis tribution, subscribers stations, a primary transmitting station, a secondary distributing station, means at the primary station for transmitting a primary carrier wave modulated with long and short intermediate carrier waves with a common single modulation on both said short and long intermediate waves and means at the secondary station for receiving said primary carrier wave, demodulating out the short and long intermediate carrier waves and amplifying and redistributing the short waves by radio and the long waves by wire to said subscribers stations.

6. In a wired system of radio broadcast distribution, a primary transmitting station with means to transmit a short carrier wave modulated with a long carrier wave, modulated to turn with a signal, regional secondary transmitting stations, means at each secondary station for receiving from the primary station, demodulating the primary carrier wave, and distributing the received matter on thelong carrier wave over wires to the subscribers stations, the transmitting means at the primary transmitting station acting to maintain the frequency of the long wiretransmitted wave length of all the secondary distributing stations the same.

7. 'In a signaling system, means for producing short waves modulated with a long wave in turn modulated with a signal, and long carrier waves bearing the same signal modulation, a wired circuit for the long carrier waves, and common receiving means arranged to receive the short wave by radio and the long wave over the wired circuit with means for first demodulating said short waves and then demodulating both long waves and adding the modulation of said long waves in a common modulation responsive means.

8. The system claimed in claim 5 with a common receiving means for both the radio and wire transmitted waves at each subscribers station.

9. A duplex receiving set having a primary input circuit tuned for short waves, a detector therein, a secondary circuit inductively connected to the output side of the primary circuit and tuned for long waves, a detector therein, and an audio receiving instrument connected to receive the output of both detector circuits, whereby either singly or doubly modulated waves may be received.

In testimony whereof I hereunto aflix my signature.

EDWARD E. CLEMENT.

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